//****************双向链表********************
class ListNode1 {
    public int val;
    public ListNode1 prev;
    public ListNode1 next;

    public ListNode1(int val) {
        this.val = val;
    }
}

public class MyTwoLinkedList {
    public ListNode1 head;
    public ListNode1 last;


    // 无头双向链表实现
    //得到单链表的长度
    public int size() {
        int count = 0;
        ListNode1 cur = this.head;
        while (cur != null) {
            count++;
            cur = cur.next;
        }
        return count;
    }

    //打印双向链表
    public void display() {
        ListNode1 cur = this.head;
        while (cur != null) {
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    }

    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key) {
        ListNode1 cur = this.head;
        while (cur != null) {
            if (cur.val == key) {
                return true;
            }
            cur = cur.next;
        }
        return false;
    }

    //头插法
    public void addFirst(int data) {
        ListNode1 node = new ListNode1(data);
        if (this.head == null) {
            this.head = node;
            this.last = node;
        } else {
            node.next = this.head;
            head.prev = node;
            this.head = node;
        }
    }

    //尾插法
    public void addLast(int data) {
        ListNode1 node = new ListNode1(data);
        if (this.head == null) {
            this.head = node;
            this.last = node;
        } else {
            this.last.next = node;
            node.prev = this.last;
            this.last = node;
        }
    }

    public ListNode1 searchIndex(int index) {
        ListNode1 cur = this.head;
        while (index != 0) {
            cur = cur.next;
            index--;
        }
        return cur;
    }

    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index, int data) {
        ListNode1 node = new ListNode1(data);
        if (index < 0 || index > size()) {
            System.out.println("插入位置不合法");
            return;
        }
        if (index == 0) {
            addFirst(data);
            return;
        }
        if (index == size()) {
            addLast(data);
            return;
        }
        ListNode1 cur = searchIndex(index);
        node.next = cur.prev.next;
        cur.prev.next = node;
        node.prev = cur.prev;
        cur.prev = node;
    }


    //删除第一次出现关键字为key的节点
    public void remove(int key) {
//        ListNode1 cur = this.head;
//        while (cur != null){
//            if (cur.val == key){
//                //是否等于头节点
//                if (cur == head){
//                    this.head = this.head.next;
//                    head.prev = null;
//                    //是否等于尾节点
//                }else if (cur == last){
//                    cur.prev.next = cur.next;
//                    this.last = last.prev;
//                    //删除的地方在中间
//                }else{
//                    cur.prev.next = cur.next;
//                    cur.next.prev = cur.prev;
//                }
//                return;
//            }else{
//                cur = cur.next;
//            }
//        }

        ListNode1 cur = this.head;
        while (cur != null) {
            if (cur.val == key) {
                //是否等于头节点
                if (cur == head) {
                    this.head = this.head.next;
                    if (head != null) {
                        head.prev = null;
                    } else {
                        last = null;
                    }
                    //是否等于尾节点
                } else if (cur == last) {
                    cur.prev.next = cur.next;
                    this.last = last.prev;
                    //删除的地方在中间
                } else {
                    cur.prev.next = cur.next;
                    cur.next.prev = cur.prev;
                }
                return;
            } else {
                cur = cur.next;
            }
        }
    }

    //删除所有值为key的节点
    public void removeAllKey(int key) {
        ListNode1 cur = this.head;
        while (cur != null) {
            if (cur.val == key) {
                //是否等于头节点
                if (cur == head) {
                    this.head = this.head.next;
                    if (head != null) {
                        head.prev = null;
                    } else {
                        last = null;
                    }
                    //是否等于尾节点
                } else if (cur == last) {
                    cur.prev.next = cur.next;
                    this.last = last.prev;
                    //删除的地方在中间
                } else {
                    cur.prev.next = cur.next;
                    cur.next.prev = cur.prev;
                }
            } else {
                cur = cur.next;
            }
        }
    }

//***********清空链表**********************
    public void clear() {
        while (head != null) {
            ListNode1 curNext = head.next;
            head.next = null;
            head.prev = null;
            head = curNext;
        }
    }

}
